1. Field of the Invention
The present invention relates to a power transmission system and, more particularly, to a system wherein input and output pawls are utilized to be driven by an input drive ring and drive an output drive ring through a plurality of different torque transmission ratios.
2. Description of the Prior Art
A variety of variable transmission systems having pulleys with varying diameters are known such as those shown in U.S. Pat. No. 1,626,701 (Sleeper) and U.S. Pat. No. 1,279,271 (Sock1). These devices contain variable pulleys associated with belt drive power transmission systems. Another type of system is shown in U.S. Pat. No. 3,956,944 which discloses a variable ratio chain sprocket where a plurality of chain engaging segments are slidably affixed first between a pair of discs and are constrained to move in a radial direction with respect thereto. There are, however, variables in this type of construction that make it difficult to precisely adjust the transmission and to avoid excessive wear. More recently, a system shown in U.S. Pat. No. 5,354,240 covers a variable transmission system utilizing in one embodiment a shifter device with a stationary shifter ring, a moveable shifter plate, and an appropriate control mechanism for selectively displacing the shifter plate with respect to the shifter ring and sprocket. While this patented device reflects a relatively new approach to variable speed transmission systems, there is a limitation with respect to the range within which the torque transmission ratio can vary.
Thus, there is a need to provide an even more efficient and greater variation in the torque transmission ratio range of such transmission system. It is to this need that the present application is directed.